The SIM800L is a low-cost module that can realise data connections and SMS via 2G network. The following explanation is limited exclusively to the SIM800L.
The configuration of the SIM800L for use with your data+ SIM card is done via AT commands via serial interface (RX & TX PINs). Please ensure that the module is connected to your Arduino, Raspberry or similar device according to the specifications. Often a voltage converter is needed to reach the required voltage and the power provided via the I/O pins might not be sufficient, leading to frequent errors..
In the Arduino IDE, there are alternative function packages for using the SIM800L that facilitate configuration via sketch.
The following AT commands can be used in this order to connect the device to the Internet:
Checks whether the serial connection is working correctly.
Activates all functionalities of the modem.
Shows with the answer READY that the SIM card is working and ready.
Activates the GPRS connection.
Sets the correct APN without username and password.
Builds the PDP Context, i.e. the Internet Session.
Outputs the assigned IP address.
This establishes a TCP connection.
Indicates that 63 characters follow in which the TCP instruction is transmitted.
GET exploreembedded.com/wiki/images/1/15/Hello.txt HTTP/1.0
An example query that retrieves the contents of a text file.
Since AT commands may differ depending on the module used, these instructions can only be used to a limited extent for modules other than the SIM800L. If in doubt, please refer to your manufacturer's documentation for the corresponding AT commands.